Add tests, fix unsigned int

tests/config.nims

@@ -1 +1 @@
-switch("path", "$projectDir/../src")
+switch("path", "$projectDir/../")

tests/test_serialization.nim

@@ -0,0 +1,46 @@
+import unittest
+
+import protobuf_serialization
+
+type
+  MyEnum = enum
+    ME1, ME2, ME3
+
+suite "Test Varint Encoding":
+  test "Can encode enum":
+    let proto = newProtoBuffer()
+    proto.encode(ME3)
+    proto.encode(ME2)
+    var output = proto.output
+    assert output == @[8.byte, 4, 16, 2]
+
+    let decodedME3 = decode(output, MyEnum)
+    assert decodedME3.value == ME3
+    assert decodedME3.fieldNum == 1
+
+    let decodedME2 = decode(output, MyEnum, offset=decodedME3.bytesProcessed)
+    assert decodedME2.value == ME2
+    assert decodedME2.fieldNum == 2
+
+  test "Can encode negative number":
+    let proto = newProtoBuffer()
+    let num = -153452
+    proto.encode(num)
+    var output = proto.output
+    assert output == @[8.byte, 215, 221, 18]
+
+    let decoded = decode(output, int)
+    assert decoded.value == num
+    assert decoded.fieldNum == 1
+
+  test "Can encode unsigned number":
+    let proto = newProtoBuffer()
+    let num = 123151.uint
+    proto.encode(num)
+    var output = proto.output
+    assert output == @[8.byte, 143, 194, 7]
+
+    let decoded = decode(output, uint)
+    echo decoded.value
+    assert decoded.value == num
+    assert decoded.fieldNum == 1